Not just for enlargements but for taking pictures without so much concern for framing the subject and instead just taking random group shots. By having more megapixels you can crop out the less desirable backgrounds or narrow the focus of the desired subject matter and still come out with a reasonably high resolution picture. Most people who use their phone for pictures are not doing so for professional purposes such as portrait photography, but more likely for business purposes such as construction, real estate, interior decorating, etc., or for family and friends photography. In either situation cropping and enlargements are quite common. If I had to choose, I would go for the higher megapixels as long as the lenses are not half bad.
There is no doubt that a 5MP camera with a good lens can result in a better picture than even a 10+ MP camera with a poor lens since it's all about quality of the optics and maximum light gathering.
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